High pressure hoses used in construction machinery and the like and conveyer belts used in transporting particulates and the like may repeatedly come in contact with surrounding metal frames and metal piping due to vibrations and the like exerted on surrounding equipment. Therefore, the high pressure hoses and the conveyer belts that are used under such conditions need to have high abrasion resistance. Covering surfaces of the hoses and the conveyer belts with a material having superior abrasion resistance such as an ultra high molecular weight polyethylene (UHMwPE) is conceivable to improve abrasion resistance, but there is a problem in that adhesiveness between some rubber compositions and the ultra high molecular weight polyethylene is low.
In order to solve this sort of problem, Japanese Unexamined Patent Application Publication No. 2003-207078A describes a hose having an outer surface rubber layer that is formed from a rubber composition having a styrene-butadiene rubber (SBR) compounded with from 10 to 50 parts by mass of a softener and/or a plasticizer as a main component and that is covered with an ultra high molecular weight polyethylene. With this hose, because the softener and/or the plasticizer permeate and wet the ultra high molecular weight polyethylene layer and promote interdiffusion and entanglement of molecules between the rubber composition and the ultra high molecular weight polyethylene during vulcanization, the adhesive strength of both components after vulcanization is improved.
However, with the hose of Japanese Unexamined Patent Application Publication No. 2003-207078A, there is a problem in that when a temperature of the hose rises greatly or the hose is subjected to large amounts of UV light from sunlight, the polymers in the rubber composition degrade, and the adhesive strength between the rubber composition and the ultra high molecular weight polyethylene decreases. When the adhesive strength decreases in this way and the ultra high molecular weight polyethylene layer peels off, visual appearance is considerably damaged, which makes it impossible to visually identify cracks and the like that may have formed on a main body of the hose. Additionally, because compatibility between the softener and/or the plasticizer and the styrene-butadiene rubber is low, the softener and/or the plasticizer that permeated the ultra high molecular weight polyethylene layer during vulcanization may bleed onto a surface of the ultra high molecular weight polyethylene layer after vulcanization. As a result, there is a possibility of not being able to distinguish this bleeding from actual damage to the hose.